COS-D
Deciding together what matters in depression care
COS-D is working out which outcomes should always be measured in depression research — the things that matter most to people living with depression, their carers, and healthcare professionals — so that different studies can be fairly compared.
What is COS-D?
COS-D — a Core Outcome Set for Depression — is a research project working out which outcomes should be measured in every study of depression treatment: what to measure (such as mood, ability to work, or social isolation) and how to measure it (which questionnaire or scale to use). It's being developed with people who have depression, their carers, and healthcare professionals — not decided for them.
Why it matters
Depression trials often measure different things, in different ways — and frequently miss what patients themselves say matters most. That makes it hard to know which treatments really work, or to combine results across studies. Agreeing on a shared set of outcomes makes depression research easier to compare, combine, and improve — for everyone involved.
Why this research is needed
Two pieces of research make the case for COS-D: a large survey of people affected by depression, and a review of how depression trials actually measure outcomes. This is the evidence behind the project — not participation in COS-D itself.
80
Outcomes identified as mattering
Patients, carers and clinicians identified 80 distinct outcomes that matter when treating depression.
Chevance et al., 2020
<25%
...of those are measured in trials
Fewer than a quarter of those 80 outcomes are actually measured in late-stage depression trials.
Veal et al., 2024/2026
388
Different measures in use
Across 450 depression trials reviewed, researchers found 388 different outcome measures in use.
Veal et al., 2024
9%
Not measured by any common scale
7 of the 80 outcomes that matter to patients — including mental pain and irritability — aren't captured by any of the 25 most-used measures.
Veal et al., 2024
These figures describe earlier research (the PROCEED study and a systematic review of depression trials) that led to COS-D. They are not current COS-D participation figures — see below for where the project stands today.
How COS-D is being developed
COS-D follows three steps. The first is complete and published; the second has a published plan but hasn't opened for participation yet; the third hasn't started.
Step 1 · Complete
Generate outcome domains
A large international survey asked people what actually matters when treating depression. It identified 80 candidate outcomes, published in 2020 as the PROCEED study.
Step 2 · Protocol published — survey not yet open
Select core outcome domains
An online survey will ask people to rate and rank the 80 candidate outcomes, followed by a consensus meeting to agree the final shortlist.
Step 3 · Planned
Select core outcome measures
A review of existing questionnaires and scales, matched against the agreed outcomes, will decide exactly how each one should be measured.
The process is overseen by a steering committee of 14 people, including three with lived experience of depression, who are co-authors of the study protocol.
Recruitment hasn't opened yet
The Step 2 survey isn't live yet. Once it is, real participation figures will appear here.
Who's involved
COS-D only works if it reflects everyone affected by depression — not just one point of view.
People with depression
Lived experience of depression, including what recovery and support feel like day to day.
Healthcare professionals
Clinical expertise from working with depression in practice, and what's realistic to measure.
Carers
The perspective of family, partners, or friends who support someone through depression.
Explore COS-D
Learn more about the study before you take part.
Want to take part?
The next stage of COS-D — open to people with depression, their carers, and healthcare professionals — hasn't opened yet. When it does, this button will take you straight to it.